An Overview of Non-minimum Phase Systems

In the realm of control theory for time-invariant systems, there exist numerous well-established design techniques aimed at stability of an equilibrium. However, in most cases, the zero dynamics of the system are disregarded as they do not determine the system’s stability. Nevertheless, the impact of zero dynamics becomes evident when the problem of tracking an arbitrary reference arises. In the case of a non-minimum phase (NMP) system, the impact of unstable zero dynamics becomes detrimental since they cannot be modified or altered. This chapter provides an overview of fundamental concepts concerning zero dynamics, including definitions, system properties related to zero dynamics, and the structural decomposition of the system that reveals the presence of zero dynamics.